JPS5982466A - Surface modification of carbon fiber - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for surface modification of carbon fibers, and in particular, the present invention relates to a method for surface modification of carbon fibers, and in particular, by treating the carbon fibers with low-temperature plasma generated by low-temperature glow discharge under specific conditions. and other materials (synthetic resins, etc.).

Due to its excellent mechanical strength, high elasticity, heat resistance, corrosion resistance, electrical conductivity, and light weight, carbon fiber is used in a wide variety of applications, including aircraft, automobiles, electronic and electric ladle materials, and sporting goods. It is used. For example, carbon fiber is an excellent reinforcing phase and is often used in combination with matrix resins such as synthetic resins.
In this case, carbon fibers have a problem of poor adhesion with the matrix resin, so it is necessary to apply a chemical treatment such as wax coating in advance.

However, even such pretreatment is not sufficient, and more effective improvement measures are desired.

In general, for composite products made of a reinforcing material and a matrix resin as described above, performance such as mechanical strength largely depends on the adhesion between the reinforcing material and the matrix resin. This improvement in adhesiveness σ) is strongly desired in the industry, where new products are eagerly awaited.

As a result of intensive research into this technical problem, the present inventors confirmed that carbon fibers can be treated with a low-temperature plasma of an inorganic gas formed under an extremely high discharge voltage. Completed the invention.

That is, in the present invention, carbon fibers are placed in an internal electrode type Ibara temperature plasma generator having a counter-discharge electrode, one of which is grounded, and 4,000 m The present invention relates to a method for surface modification of carbon fibers, which is characterized in that carbon fibers are treated with low-temperature plasma generated by applying a discharge voltage of volts or higher to cause glow discharge.

According to the above-mentioned method of the present invention, the surface of carbon fiber is modified and the adhesion between it and other flanks is significantly improved. The composite product used as a reinforcing material has the effect of significantly improving mechanical and electrical properties compared to conventional products.

Carbon fibers targeted by the present invention include filaments, multifilament yarns, chopped fibers, cloth fibers, and the like, and there are no particular restrictions on their forms.

The above-mentioned modification treatment of the carbon fibers is carried out using 03: Hori plasma generated by performing glow discharge while flowing an inorganic gas under reduced pressure in the internal electrode type low temperature plasma generator having the above-mentioned counter-discharge electrode. However, the meaningless gases used here are helium, neon, argon,
Examples include enzymes, nitrogen, nitrous oxide, -nitric oxide, nitrogen dioxide, -carbon oxide, carbon dioxide, cyanide odors, diluted sulfuric acid gas, and hydrogen sulfide. The above ingredients are heated and used. In invention X, it is preferable to use oxygen gas or a gas containing at least 10% by volume of oxygen gas as the inorganic gas. Incidentally, an organic compound gas may be mixed with these inorganic gases, but the mixing ratio should be kept within a small range.

The pressure of the gas atmosphere in the device is preferably in the range of 0.001 to 10 Torr (particularly 0.0 l-1 Torr), and under such gas pressure, the pressure of the gas atmosphere at a frequency of 1
At high frequencies from 0 KHz to 100 MHz, IOW ~ 10
Stable glow discharge 1 can be performed by applying 0 KW of power. In addition to the above-mentioned high frequency, low frequency, microwave, direct current, etc. can be used as the frequency band.

In the present invention, it is preferable that the device is an internal electrode type,
Depending on the case, it may be an external electrode type, or it may be a coil type, capacitive coupling, or inductive coupling.

There is no particular restriction on the shape of the electrodes, and both counter electrodes may have a back I-shape or a different shape, and they can be in various shapes such as a flat plate, a ring shape, a rod shape, a cylinder shape, etc. Place the metal inner wall of the device on one side! I! It may be of a type that is closed and grounded.

In the method of the present invention, however, the plasma is generated by causing a gummy discharge by applying a discharge voltage of 4,000 volts or more between the counter discharge electrode while circulating an inorganic gas under reduced pressure. ), and low-one-product plasma treatment under these conditions brings about a remarkable adhesion-improving effect on the above-mentioned carbon fibers (filament, multifilament yarn, chopped, cloth, etc.). This improvement in adhesion increases as the discharge -F+- is further increased, for example to 5,000.7.000.10,000 volts. On the other hand, the release? jj tg
Although some adhesion improvement can be achieved when the IF is less than 4,000 volts, the effect is low and long treatment times are required to achieve sufficient adhesion modification effect)!
j, which is economically disadvantageous. Note that as the discharge type IE increases, the amount of heat generated increases and energy loss also increases, so it is necessary to select optimal conditions in terms of cost.

Applying a voltage of 4,000 volts or more between the counter discharge electrode,
In order to maintain stable low-temperature plasma, it is necessary to cover the input electrode with an insulating coating that has a considerable withstand voltage. For example, with exposed metal electrodes such as copper, iron, aluminum, etc., the discharge current has priority, and the discharge voltage is 1,000
The limit is around 0 volts, and the discharge is unstable.
Furthermore, it has little effect on improving the surface adhesion of carbon fibers, which is the object of the invention.

The insulating coating of the electrode is preferably a hollow foot, glass coat, ceramic coat, etc. for electrodes made of iron, iron, aluminum, etc., and the withstand voltage when applying direct current is 10,000 volts/■ or more. This is desirable.

The conditions for stably maintaining the generation of low-temperature plasma by applying a discharge voltage of 4,000 volts or more between the logarithmic electrodes and causing glow discharge are as follows: In addition to ~10 Torr, the power consumption density of the discharge electrode surface is 25 Watts) / cn? per unit area of the input electrode. Above, the distance between the electrodes is 1 to 2
It is preferable to set it to 0 cm. When the gas pressure increases by 10 Torr or more, the high η increases to generate Iha vortex plasma.
It requires a lot of force and generates a lot of heat, and in the following 11 cases, the discharge becomes unstable, and in either case, the effect of improving adhesion is low, which does not meet the purpose of non-invention. . If the power consumption density of the discharge electrode surface is less than 25 W/C, it will be difficult to maintain the high power density that is the object of the present invention, and no improvement in adhesion will be obtained. Furthermore, if the distance between the electrodes is less than 1 cm, the thermal influence of the electrodes will become undesirable and cause operational difficulties, while if it is more than 20 cm, the power loss will increase due to the design of the device. However, in order to solve this problem, it is necessary to increase the capacity of the device, which is not economically desirable.

Modification by low-temperature plasma treatment generated by low-temperature glow discharge is characteristically limited to only the surface layer.

Therefore, the carbon fibers targeted by the present invention have improved adhesion without losing their excellent inherent properties.
11Tx resin to form a composite material with excellent mechanical and electrical properties, and this product is an excellent product with a 200% increase in shear strength, which is a measure of adhesive strength.

Next, specific examples will be given, but the present invention is not limited thereto.In the examples listed below, all of the low-temperature plasma generators shown in the drawings were used. Processing tank 1 in the figure is made of stainless steel.
This is designed to be able to reduce the pressure to 0.001 Torr using a vacuum pump 2. A gas introduction pipe 8 is attached to the processing tank 1, and various processing gases are divided as necessary and introduced into the tank. A rotating stainless steel cylindrical cathode 4 is installed in the processing tank 1, and the rotation speed of this cylindrical cathode can be continuously adjusted by a drive device 5. This cylindrical cathode 1 is electrically grounded to the earth through one processing tank. Further, this rotary cylindrical cathode has a structure in which the temperature can be adjusted by passing hot or cold water inside the cathode. Furthermore, the inside of the processing tank 1 is electrically insulated from the tank.
A rod-shaped electrode 6 is provided, and is spaced from the cylindrical cathode 4 at equal intervals. Furthermore, a Villany vacuum gauge 7 is attached to the processing tank 1 to measure the pressure inside the processing tank 1.

Further, a high frequency power source 8 is provided to apply high frequency power between the electrodes. and a high voltage probe (Iwasaki Tsushinki Co., Ltd. HV-p-30) 9 for measuring hQ[L voltage.
A current probe (Iwasaki Tsushinki Co., Ltd. CP-502) IO and a determination (Iwasaki Tsushinki Co., Ltd. CP-512) 11 for measuring the discharge current are attached to the synchroscope 12 for observing two phenomena. It is connected.

The peak value CV > of the discharge voltage can be determined as the product of the voltage value obtained from the tube surface amplitude of the synchroscope and the reciprocal of the attenuation amount of the probe. The discharge current can be determined as the product of the voltage value read from the tube surface amplitude of the synchroscope and the current sensitivity of the termination.

The phase difference between the discharge current and the discharge voltage can be determined from the difference between the current waveform and voltage waveform on a synchroscope.

If the discharge current and discharge voltage can be regarded as a sine wave, the discharge power P is] ”-E4- C!03ψ P: Discharge power (W) E: Discharge voltage (p-p peak value) (V) ■=Discharge current (T)-1) Peak value) (A) ψ: It can be determined from the phase difference between the discharge current and the discharge voltage.

Example 1 High strength carbon fiber obtained by carbonizing polyacrylic trill fiber (diameter 7μ, tensile strength 280 KP/m
, elastic modulus 23. A surface-untreated multifilament yarn of OOO [7/m) was wound around the cylindrical cathode of the low-temperature plasma processing apparatus shown above, and the pressure inside the processing tank was reduced. After the internal pressure becomes 0.001), oxygen gas 3 Q Q
N+fi/min was introduced through the gas inlet tube to bring the internal pressure to 0.1 Torr.

By adjusting the output power of the high-frequency power source during discharge treatment, the point-to-point distance between the electrodes (p-p) can be reduced to 2,000.
．． 3,000.4,000.5,000°7.000.
The voltage was changed to 10,000 volts. The input power at each time is 1.2 KW, 2. 'OKW, 2.9
KW, 3.9 KW, 6.6 KW, 14.4 xw
Met. Since the discharge area was 500 d, the discharge power density per unit area was 2.4 W/aI! ? , 4
．． OW /crt15.8 W/ e11? , 7.8
W/crl, 13.2 W/art.

It is 28.8W/arF. At these discharge powers, the total discharge processing power is 40 W・sec/d, 80 W・sec/d, 1
The processing time was adjusted to 60 W-sec/cnr, 320 W, sec/al. However, in this example, the discharge frequency was 200 KHz, and the distance between the electrodes was 5 cm.

After one side of the filament yarn had been treated as described above, the back side of the filament yarn was similarly plasma treated under the same conditions.

The filament yarns treated with low-temperature plasma on both sides were woven into a plain weave cloth, and then epoxy resin (Amerioan Cy) was woven using the hand lay-up method.
anamid BP-907) and cured at room temperature. The volume content of carbon fiber in this composite molded product was 60%. Table 81 shows the results of a tensile test of this molded product based on J-K 5K7113.

As shown in Table 1, by subjecting carbon fiber to low-temperature plasma treatment under the above conditions, the tensile strength of the composite with epoxy resin is significantly improved. Peak voltage between electrodes is 30
Under 00 pol, a significant improvement in tensile strength increases the total power of the discharge treatment and C+ cannot be obtained, but the peak voltage between the electrodes is 400 por.
Exceeding 0pol)Y significantly improves the tensile strength. In this case, the tensile strength can be sufficiently improved even if the total electric power for the discharge treatment is small.

Example 2 High-strength carbon fiber obtained by carbonization treatment of polyacrylonitrile fiber (surface-untreated multifilament yarn with a diameter of 7 μm and a tensile strength of 280 sand/-1 and a modulus of elasticity of 23.0001%/rri). It was wrapped around the cylindrical cathode of the plasma processing apparatus shown earlier, and the pressure inside the processing tank was reduced.The internal pressure was 0.
．． 001) After reaching 300 ml of argon gas in the tank
N-7 minutes and oxygen gas 300 Nd1 minutes were introduced from the gas introduction tube to bring the internal H- to 0.4 Torr.

By adjusting the output power of the high frequency power source during the discharge process, the peak voltage between the electrodes (p-pv) can be adjusted to 2,000
0.3,000,4,000.5,000.7.000
, No., 000 volts. At this time, each input power is 1. OKW, 1.5KW.

2.3KW, 3. The IKW was 5.3KW and 11.6KW. Since the discharge area was 500 d, the discharge power density per unit area was 2 W/cr&, 3'W/7.4.
6W/an? , 6.2 W/i, 10.6 W/7.2
It is 3.2 W/d. At these discharge powers, the total discharge processing power is] 60 W・sec/cn? The processing time was adjusted so that it remained constant. The discharge frequency tj13 at this time.
The frequency was 56 MHz, and the distance between the electrodes was 3 cm.

After one side of the filament yarn had been treated as described above, the back side of the filament yarn was similarly plasma treated under the same conditions.

Filament yarn treated with low-temperature plasma on both sides in this way? It was cut into lengths of 3 to 6 m, mixed with nylon 66 and 1 fat, and cross-wire-shaped using an extruder to form pellets. The amount of carbon fibers contained in this pellet was 30%.

This pellet is molded using a normal injection molding process,
A rod-shaped molded body was made. Regarding this rod-shaped sample, JIS K
Table 2 shows the results of tensile WA and aging performed after blocking 7113.

Table 2 As shown in Table 2, the tensile strength of the nylon 66 resin composite molded article using plasma-treated carbon fiber is remarkable. Moreover, when the peak voltage between the electrodes exceeds 4.000 pol)Y, the tensile strength is significantly improved.

Example 3 A plain-woven cloth made of surface-treated carbon fiber similar to Example 3 was wrapped around the cylindrical cathode of the low-temperature plasma processing apparatus shown above, and the pressure inside the processing tank was reduced. After the internal pressure reached 0.001), nitrogen gas and oxygen gas were introduced into the handle. The total flow rate of the two types of gas is 100Nd/
minute, and the internal pressure was 0.1 torr.

The mixing ratio of oxygen (0□) gas and nitrogen (N2) gas is 0
: 100.5 : 95, 10:90, 20:80
．． 40:60, 60:40, 80:20,
The ratios were 90:10 and 100:0.

The peak voltage between the electrodes is constant at 7.0 (10 volts), and the distance between the electrodes is 4 cu+. The processing time is 40 seconds after operation, and the discharge frequency is 110 KHz.

Cross'h-iA+ k O! :
After treating the cloth with M plasma, the back of the cloth [
7i'r plasma treatment. This plasma-treated cloth was molded using an epoxy resin (used in Example 1) by the hendry-up method and cured at room temperature. The carbon fiber content in this molded product was 60'/n in volume ratio.

This molded product was subjected to a tensile test based on JIS K 7]13, and the results are shown in Table 3.

Table 3 As shown in Table 3, the strength of molded products using plasma-treated carbon fibers is significantly improved. The strength is significantly increased by f2.

[Brief explanation of drawings]

The drawing is a schematic configuration diagram showing an example of an internal electrode type low temperature plasma generation device. l... Stainless steel treated cypress, 2... Body pump. 3... Gas introduction tube, 4... Cylindrical cathode, 5... Drive device, 6... Rod-shaped electrode, 7... Pirani vacuum needle, 8... High frequency power supply, 9... Straight weight ” probe, 1o
...Current probe, 11... Termination, 12... Synchronoscope for observing 2 phenomena. Patent applicant 4H Etsu Chemical Industry Co., Ltd.

Claims (1)

[Claims] 1. Carbon fibers are placed in an internal electrode type low-temperature plasma generator that has a counter-discharge electrode, one of which is grounded, and a voltage of 4,000 volts or more is applied between both electrodes while flowing inorganic gas under reduced pressure. A method for surface modification of carbon fibers characterized by treatment with low-temperature plasma generated by applying a discharge voltage to cause glow discharge.